1. Field of the Invention
The present invention relates to a semiconductor laser diode package, and more particularly, to a semiconductor laser diode package containing a high output power semiconductor laser diode with a long cavity length.
2. Description of the Related Art
Compact, low threshold current semiconductor laser diodes have been widely used in communication applications or high-speed data transmission and data recording and reading in an optical disc player.
FIG. 1 is a cross-sectional view of a conventional semiconductor laser diode package. Referring to FIG. 1, the conventional semiconductor laser diode package includes a stem 10, a heat sink 12 projecting from one side of the stem 10, a semiconductor laser diode 15 that is mounted on the heat sink 12 and generates a laser beam, and a plurality of connecting pins 11 that are fit into the other side of the stem 10 and electrically coupled to the semiconductor laser diode 15. A cap 20 is attached onto the one side of the stem 10 and covers the heat sink 12 and the semiconductor laser diode 15. A window 22 through which the laser beam emitted by the semiconductor laser diode 15 exits is attached to the center of the cap 20.
A semiconductor laser diode being developed as a light source for high-speed optical disc systems needs to have a narrow and a long cavity (e.g., greater than 1.5 mm) in order to obtain high output power and good thermal characteristics.
However, a semiconductor laser diode with a long cavity length is structurally difficult to apply to the conventional laser diode package of FIG. 1 to achieve compatibility with an existing optical system (for a semiconductor laser diode package currently being used as standardized light source for optical disc systems, the length of a stem is about 1.41 mm). Furthermore, in the case of a high power semiconductor laser diode currently being used, a very high intensity beam is emitted from the rear facet of the diode. When the high power semiconductor laser diode is applied to a conventional semiconductor laser diode package, the beam emitted from the rear facet of the laser diode is reflected and dispersed back to the light-emitting facet of the diode, causing interference between the beams. The interference will likely increase the noise level and produce unstable output.